The "car detector" I mentioned is the same as a traffic signal loop detector. BTW the PLCs I have had experience with are far from delicate. I think they are too pricey for this application, though. Multiple LED-phototransistor pairs could be wired with all the LEDs in series and all the phototransi...

Looking for inductance change should work but I think you want the axis of your coil vertical. When a train is present part of the flux path that is normally entirely through air will be through iron. You might be able to modify a metal detector. A car detector of the sort used at parking lot entran...

Ok, I'm sure this is going to be a stupid question but I'm drawing a blank, so here goes. A job requiring softjaws is about to commence. I have softjaws and a spider but how does one measure the diameter of the softjaw cut. All of my micrometers measure at 180 degrees whether they be calipers or mi...

Spot welders are quite different from arc welders. They rely on resistance heating in the parts being welded rather than on arc heating. This requires that you firmly clamp low-resistance contacts directly at the spot where you want the weld. The open circuit voltages are quite low (on the order of ...

Depends on what you mean by a "true" rotary converter. Driving a synchonous three-phase generator with a DC motor controlled so as to keep the frequency correct would give you perfect separately-derived power. Converters built using a single three-phase motor, some capacitors, and some relays can wo...

The construction companies belonged to two different Mafia families, and they didn't communicate well. The concrete is also problematic because it's full of dead guys named Vinnie. Mob, not Mafia. It's in Chicago. Plausible explanation: Due to some oversight such as a failure to read some Federal r...

I've also been very satisfied with Speedy Metals. Since they are just on the other side of Wisconsin from me I can get 2nd day delivery from them via Spee-Dee Delivery (you have to place the order by phone and request Speed-Dee) for about half of what UPS would charge for their regular ground rate. ...

Steve writes: First think I thought when I saw it was the brush on the rubber band of a VanDeGraff generator. I can picture my hair standing on end while running the saw. Can't happen. The brush touches the steel blade which is conductive and so won't carry a static charge and the blade is also elec...